This application is based on and incorporates herein by reference Japanese Patent Application Nos. Hei 9-106282 filed on Apr. 23, 1997, and Hei 9-198833 filed on Jul. 24, 1997.
1. Field of the Invention
The present invention relates to a heat exchanger for heating a passenger compartment of a vehicle by carrying out heat exchange between air and hot water (engine coolant).
2. Description of Related Art
Conventionally, in an air conditioning apparatus for a vehicle, an air conditioning unit 4 is disposed below an instrumental panel 3, as shown in FIG. 29. The instrumental panel 3 is disposed at the front portion of a passenger compartment 2 in the vehicle 1. The air conditioning unit 4 includes a blower, a cooling heat exchanger, and a heating heat exchanger, and so on. In the heating heat exchanger, hot water flows from a vehicle engine 5.
According to an above-described layout of the air conditioning unit 4, because a height dimension xe2x80x98hxe2x80x99 of the air conditioning unit 4 is comparatively large, a heating heat exchanger 11 in which tanks 12, 13 are provided on both upper and lower portions of a heat-exchanging core portion 11, as shown in FIG. 11, can be applied. In such a heat exchanger, the height dimension H and the width dimension W are about 150-300 mm. Thus, the hot water flows vertically in the heat-exchanging core portion 11, and the temperature of air passing through the heat-exchanging core portion 11 is made uniform in the width (W) direction (right and left direction) of the core portion 11.
Recently, in a vehicle air conditioning apparatus, so a called a module structure is demanded. In the module structure, the instrumental panel 3 is first equipped with the air conditioning unit 4 and some instrumental elements, and the instrumental panel 3 equipped with these elements is then installed in the vehicle.
When the module structure is applied, as the air conditioning unit 4 and the instrumental elements are equipped to the instrumental panel 3 in a manufacturing process, the vehicle installation is simplified. Further, an entire space where these elements are provided is downsized, thereby increasing available space in the passenger compartment.
According to a study by inventors of the present invention about the module structure, integrating the air conditioning unit 4 and the instrumental panel 3 so that the air conditioning unit 4 is, as shown in FIG. 29, formed into rectangular shape extending along the instrumental panel 3 in the width direction of the vehicle is a superior configuration.
In such an air conditioning unit 4, the width dimension (right and left dimension of the vehicle) of the air conditioning unit 4 is much larger the height dimension xe2x80x98hxe2x80x99. Therefore, the heating heat exchanger 10 is also formed into the rectangular shape like the air conditioning unit 4, as shown in FIG. 30A. For example, the height dimension H is about 100 mm, and the width dimension W is about 500 mm.
As a result, as shown in FIG. 30A, the tanks 12, 13 need to be disposed at both side ends of the heat-exchanging core portion 11 in the width direction thereof for downsizing the height dimension H. Thus, the hot water flows in the heat-exchanging core portion 11 in one way in the width direction thereof.
However, because the length of a hot water passage from a hot water inlet side to a hot water outlet side is long in the heat-exchanging core portion 11, the hot water temperature is much lowered at the hot water outlet side in comparison with at the hot water inlet side. As a result, the difference of the discharged air temperature in the width direction becomes large, thereby deteriorating the effects of air conditioning.
For reducing the difference of the discharged air temperature, as shown in FIG. 30B, it is considerable to provide a hot water inlet tank 14 and a hot water outlet tank 15 at one side end of the core portion 11 while being partitioned in the upper and lower direction, and to provide an intermediate tank 16 where the hot water U-turns at the other side end of the core portion 11.
According to this structure shown in FIG. 30B, the hot water flows from the left side to the right side in the lower half portion of the heat-exchanging core portion 11, and flows in reverse from the right side to the left side in the upper half portion of the heat-exchanging core portion 11. Thus, the difference of the discharged air temperature in the width direction of the core portion 11 can be reduced.
However, the length of the hot water passage in the structure shown in FIG. 30B is twice as long as that in the structure shown in FIG. 30A. Thus, the hot water flow resistance is increased in the heat-exchanging core portion 11, thereby reducing the hot water amount and deteriorating heating performance.
An object of the present invention is to provide a heat exchanger a width dimension of which is much larger than a height dimension, in which an heat-exchanging medium flow resistance in a heat exchanging core portion is suppressed from increasing, and discharged air temperature is made uniform in the width direction of the heat-exchanging core portion.
According to the present invention, the heat-exchanging core portion is divided into a first core portion and a second core portion. Heat-exchanging medium flows in the first core portion and the second core portion in an opposite direction to each other.
Thus, even when the heating heat exchanger, the width dimension of which is much larger than the height dimension, is used, the air temperature is prevented from varying in the width direction. Further, as the heat-exchanging medium flows in the first and second core portions in parallel, the heat-exchanging medium flow resistance is suppressed from increasing.